The invention is directed to the continuous production of pentanediol-1,2 from pentene by oxidizing it to pentene oxide-1,2 and saponifying this epoxide with water to form pentanediol-1,2.
Pentanediol-1,2 is useful as an intermediate in the production of fungicides.
Mention of the production of pentanediol-1,2 is found, e.g., in German patent No. 2,205,023 which describes a one-step process for the simultaneous expoxidation and saponification of higher olefins, i.e., olefins, which preferably should have at least 4 carbon atoms. This one-step process uses aqueous percarboxylic acid solutions, both for the epoxidation and the saponification. However, there is required considerable amounts of water, which is particularly expensive in carrying out the process.
According to U.S. Pat. No. 3,475,499, there is described a two-step process for the production of 1,2-epoxides and saponification to the corresponding diols in which the epoxidation can be carried out continuously with hydroperoxides in the presence of organic solvents such as hydrocarbons. However, these hydrocarbons should be distilled off, preferably before the saponification.
According to this patent, the epoxide containing sump resulting from the distillation of the epoxidation mixture is saponified with water in the presence of alkaline or acid catalysts. According to Example 1 which is directed to a C.sub.11 -C.sub.15 -olefin cut the yield of epoxide is only 45%; it is saponified together with the unreacted olefin.
Although the selectivity is higher thereby the amount of pure diol, due to the low yield of epoxide, is moderate and is industrially non-interesting.
Thus, it is the task of the invention to develop a low cost industrial continuous process for the production of pentanediol-1,2 by epoxidizing pentene-1,2 and subsequent saponification of the resulting epoxide in aqueous medium with an industrially satisfactory yield and with very good selectivity.